Two trains, one behind the other
Two trains go the same way; the second starts behind the first and is faster. Find when it catches up.
2D
Age 10+10 min
Motion problems
Loading simulation…
Press “Run”. Bodies move by the laws of physics: gravity, friction, elasticity.
What the experiment shows
The trains start from two stations whose distance is set by a slider. The second is faster and closes the gap.
How to run it
- Run the scene: the chaser gets closer and the S caption shows the gap.
- Enter your answer in the Task panel and press “Check”.
- Change the speeds or the head start with the sliders: will the fast one catch up sooner or later?
Questions to discuss
- Why does the gap shrink by the difference of the speeds, not the sum?
- What happens if the speeds are almost equal?
The science
While one moves ahead the other chases: every hour the head start shrinks by the difference of the speeds, the closing speed in a chase. The chase time is t = head start / (v₂ − v₁).
Try it at home
Let a friend start 10 steps ahead while you walk a bit faster: how many steps do you need to catch up?
What to change in the editor
- Open the example in the editor and add a third participant who leaves even later.
- Swap the speeds so that catching up is impossible and explain why.